Turbine wheelspace temperature control

ABSTRACT

Apparatus for controlling an amount of cooling air provided to a wheelspace of a turbine section of a gas turbine includes a sensor that senses a temperature of the wheelspace and provides a sensed temperature signal. The apparatus also includes a processor, responsive to the sensed temperature signal, that determines if the temperature of the wheelspace exceeds a desired value. If the temperature of the wheelspace exceeds the desired value, the processor activates an actuator control signal to control movement of a cooling air control valve to allow a greater amount of cooling air sourced from a compressor section of the gas turbine or from a cooling air cooler which receives air from the compressor section of the gas turbine to flow to the wheelspace, thereby cooling the temperature of the wheelspace.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates to gas turbines and, inparticular, to control of the temperature of the wheelspaces of aturbine section of a gas turbine through control of the cooling airflowprovided to the wheelspaces.

Turbine wheelspaces are those cavities or areas in the turbine sectionof a gas turbine located between the turbine rotor discs or wheels thatsupport corresponding rows of turbine blades. The wheelspaces arelocated radially inward of the mainstream flow of gas through theadjacent turbine stages. Typically, the radially inward discs are heatedby various effects, including conduction through the rotor blades,ingress of mainstream flow into the wheelspace cavities, and windageheating within the wheelspaces.

The actual turbine wheelspace temperatures are in general a function ofturbine output, ambient temperature and unit degradation or condition.Wheelspace temperatures are typically sensed or monitored and alarms maybe used to signal higher than acceptable temperature readings. Gasturbine operators may reduce power to prevent such alarms from occurringdue to unacceptably high wheelspace temperatures. However, this practicecauses a loss of revenue and potentially limits total plant output onrelatively hot days.

Another method for achieving reductions in wheelspace temperaturesincludes shutting the gas turbine down, changing orifice plates in thecooling supply circuit, and then restarting the gas turbine. Thisprocedure, however, causes shutdown and startup delays, and requiresfrequent adjustment as a function of the outside ambient temperature.

A further method for adjusting wheelspace temperatures includes areduction in cooling flow, thereby having the effect of increasingwheelspace temperatures. Setting relatively higher wheelspacetemperatures results in increased performance; however, it may alsoreduce the life cycle of the gas turbine.

It is also known to provide cooling airflow to the wheelspacessimultaneously in series or in parallel with cooling airflows providedto other components of the gas turbine. However, a problem with someembodiments of this practice, even with variable cooling airflows, isthat if adequate cooling airflow is provided to the wheelspaces thentypically the cooling airflow provided to other gas turbine components(e.g., turbine nozzles, diaphragms, shrouds) may be insufficient foradequate cooling of those other components.

BRIEF DESCRIPTION OF THE INVENTION

According to one aspect of the invention, apparatus for controlling anamount of cooling air provided to a wheelspace of a turbine section of agas turbine includes a sensor that senses a temperature of thewheelspace and provides a sensed temperature signal. The apparatus alsoincludes a processor, responsive to the sensed temperature signal, thatdetermines if the temperature of the wheelspace exceeds a desired value.If the temperature of the wheelspace exceeds the desired value, theprocessor activates an actuator control signal to control movement of acooling air control valve to allow a greater amount of cooling airsourced from a compressor section of the gas turbine or from a coolingair cooler which receives air from the compressor section of the gasturbine to flow to the wheelspace, thereby cooling the temperature ofthe wheelspace.

According to another aspect of the invention, apparatus for controllingan amount of cooling air provided to a wheelspace of a turbine sectionof a gas turbine includes a sensor that senses a temperature of thewheelspace and provides a sensed temperature signal. The apparatus alsoincludes a processor, responsive to the sensed temperature signal, thatdetermines if the temperature of the wheelspace is below a desiredvalue. If the temperature of the wheelspace is below the desired value,the processor activates an actuator control signal to control movementof a cooling air control valve to allow a lesser amount of cooling airsourced from a compressor section of the gas turbine or from a coolingair cooler which receives air from the compressor section of the gasturbine to flow to the wheelspace, thereby allowing the temperature ofthe wheelspace to increase.

These and other advantages and features will become more apparent fromthe following description taken in conjunction with the drawings.

BRIEF DESCRIPTION OF THE DRAWING

The subject matter, which is regarded as the invention, is particularlypointed out and distinctly claimed in the claims at the conclusion ofthe specification. The foregoing and other features and advantages ofthe invention are apparent from the following detailed description takenin conjunction with the accompanying drawings in which:

FIG. 1 is block diagram of a gas turbine having embodiments of theinvention located therein;

FIG. 2 is cross section of a portion of a turbine section of a gasturbine that includes an embodiment of the invention; and

FIG. 3 is a cross section of a portion of a turbine section of a gasturbine that includes another embodiment of the invention.

The detailed description explains embodiments of the invention, togetherwith advantages and features, by way of example with reference to thedrawings.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1 is a gas turbine 10 that includes a compressor section 12,which provides compressed air. The compressor 12 may be axially alignedwith a turbine section 14 of the gas turbine 10 on a single shaftrepresented by a longitudinal centerline 16. Most of the compressed airmay be supplied to the turbine combustors (not shown), but some of thecompressed air may be extracted for other uses. For example, cooling airmay be extracted from the compressor 12 at extraction ports 18, andsupplied via lines (e.g., pipes, ducts, etc.) 22, 24 to selected areasof the turbine section 14 and ultimately to the wheelspaces (FIGS. 2-3)within the turbine section 14 via inlet ports 26, 28, 30, 32, (e.g.,holes in the turbine casing) in accordance with embodiments of theinvention, as described in more detail hereinafter and illustrated inFIGS. 2-3. In an alternative embodiment, a cooling air cooler 33 may beprovided in one of the lines 24 and located external to the gas turbine10. Cooling air sourced from the compressor section 12 on the line 24may be provided to the cooling air cooler 33, which further cools thecompressed air that is then provided to the corresponding input ports26, 28. In a similar manner, cooling air may be extracted fromcompressor ports 34, 36 and supplied via lines 38, 40 (e.g., pipes,ducts, etc.) and ultimately to the wheelspaces within the turbinesection 14 via inlet ports 42, 44, 46, 48, (e.g., holes in the turbinecasing) also in accordance with embodiments of the invention, asdescribed in more detail hereinafter and illustrated in FIGS. 2-3.

Embodiments of the invention may include a feedback control loop tocontrol the wheelspace temperature to above or below desired lower andupper limits or values, respectively (e.g., within an acceptable rangeof values). Thus, embodiments of the invention may include amicroprocessor 50 or other suitable type of processor, computing orlogic circuit. The microprocessor 50 is responsive to one or moresignals on corresponding signal paths 52, such as at least one of wiredor wireless lines or the like that establish each of the paths 52, orcombinations thereof. Each signal on the corresponding signal path 52 isdirectly or indirectly indicative of the temperature of a correspondingwheelspace as provided by a suitable temperature sensor located in thewheelspace (FIGS. 2-3). However, other suitable sensed signals may beused that directly or indirectly indicate the temperature of thewheelspace. As described in more detail hereinafter with respect toFIGS. 2-3, the microprocessor 50 is responsive to the wheelspacetemperature signals to provide one or more actuator control signals oncorresponding signal paths 54, such as at least one of wired or wirelesslines or the like that establish each of the paths 54, or combinationsthereof. The actuator control signals are utilized to control the amountof cooling airflow from the compressor for control of the temperature ofeach of the various wheelspaces to desired or acceptable values.

In FIG. 2 is an embodiment of the invention in which a hole is formedthrough the solid (e.g., cast iron) turbine casing 60 and into an innercavity or plenum 62. Disposed through the hole is one of the lines(pipes, ducts, etc) 22, 24, 38, 40, which provides the compressed airfrom the compressor 12 (FIG. 1) into the open area plenum 62. Thecompressed air in the plenum 62 flows unrestricted downward in FIG. 2into a hollow nozzle 64, which may be airfoil shaped, as is known. Thatsame compressed air may also flow unrestricted down into an open areadiaphragm 66. As described in detail hereinafter, the compressed airthat enters the plenum 62 is utilized to control the temperature of acorresponding wheelspace 68 illustrated in FIG. 2 within the turbinesection 14 (FIG. 1), in accordance with an embodiment of the invention.

One or more temperature sensors 70 may be located within each one of thewheelspaces 68. Each wheelspace 68 may be an uninterrupted 360-degreecircumferential cavity in the turbine section 14 of the gas turbine 10(FIG. 1). Since the turbine section 14 (FIG. 1) typically has multiplerows of turbine blades, there exists a multiple number of wheelspaces 68between the rows of blades. The sensor 70 may be any suitable type ofsensor that senses the temperature of the wheelspace 68 either directlyor indirectly and provides the wheelspace temperature signal on thesignal path 52 to the microprocessor 50. In accordance with anembodiment of the invention, when the microprocessor 50 determines thatthe then-current temperature of any one or more particular wheelspaces68 is greater than a desired or acceptable upper value (for example, bycomparing the sensed wheelspace temperature to a desired one or morevalues, e.g., stored in a memory associated with the microprocessor 50),the microprocessor 50 activates the actuator control signal on thesignal path 54 to ultimately reduce the temperature of that particularwheelspace 68 to a desired value.

Embodiments of the invention may also have the microprocessor 50determine if the then-current temperature of any one or more particularwheelspaces 68 is less than a desired or acceptable lower value using,e.g., a similar comparison method. If the sensed temperature is lessthan the desired value, the microprocessor may activate the actuatorcontrol signal on the signal path 54 to ultimately increase thetemperature of that particular wheelspace 68 to a desired value.

The actuator control signal on the signal path 54 may connect to adevice 72, such as an electromechanical device (e.g., a motor), ahydraulic actuator or other suitable device. The output 74 of the device72 may connect to an optional synch ring 76, which may be contiguous andencircle the entire circumference of the turbine section 14 of the gasturbine 10 (FIG. 1). The synch ring 76, if utilized, connects to eachone of a plurality of actuators 78 located outside of the turbine casing60. One such actuator 78 is shown in FIG. 2. The output shaft of theactuator 78, which may be rotatable or movable is some other suitablemanner, connects to a shaft 80 that may also be rotatable or movable insome other suitable manner. The shaft 80 connects at its bottom end (asviewed in FIG. 2) located within the plenum 62 to a cooling air controlvalve 82 having one or more oblong (or other suitable) shaped openings84. The valve 82, which may be located within the plenum 62, may berotatable or movable in some other suitable manner. The cooling aircontrol valve 82 may also comprise other suitable types of valves, suchas a butterfly valve, a gate valve, or a ball valve. Seals and/orbushings 86 are provided to properly seal the shaft 80 at its connectionwith the output of the actuator 78. A bushing 86 is also placed througha hole formed (e.g., drilled) in the turbine casing 60 to provide a sealaround the shaft 80. The seals and/or bushings 86 reduce leakage ofcompressed air gasses from the inside of the turbine casing 60 to theoutside of the casing 60.

A tube 90 is located within the hollow nozzle 64 and in the diaphragm66. The top or upper portion of the tube 90 (as viewed in FIG. 2) alsohas one or more oblong (or other suitable) shaped holes 92 in the samegeneral vertical location as the holes 84 in the bottom portion of theshaft 80. The bottom portion of the tube 90 has a narrower diameterportion that is in fluid communication with the wheelspace 68.

In operation, when the microprocessor 50 determines that thethen-current temperature of a particular wheelspace 68 is greater than adesired or acceptable upper value, the microprocessor activates theactuator control signal on the signal path 54, which ultimately causesthe holes 84 in the cooling air control valve 82 to line up (eitherfully or partially) with the holes 92 in the upper portion of the tube90. When lined up as such, this allows an amount of the compressed airin the plenum 62 to flow into and down through the tube 90 andultimately into the wheelspace 68. This compressed air is typicallycooler than the sensed hotter air in the wheelspace 68 that exceeded anupper value and caused the flow of the cooling compressed air to thewheelspace 68 to occur, thereby reducing the temperature of thewheelspace 68. Once the microprocessor 50 determines that the wheelspacetemperature is equal to or below an upper value and, thus, is at anacceptable value, the microprocessor then activates the actuator controlsignal on the signal path 54 to cause the cooling air control valve 82to move and, thus, cause the holes 84 in the valve 82 to not align, oronly partially align, with the holes 92 in the upper portion of the tube90. This stops or reduces the flow of the cooling compressed air to thewheelspace 68 through the tube 90.

Similarly, when the microprocessor 50 determines that the then-currenttemperature of a particular wheelspace 68 is less than a desired oracceptable lower value, the microprocessor activates the actuatorcontrol signal on the signal path 54, which ultimately causes the holes84 in the valve 82 to line up (either partially or not at all) with theholes 92 in the upper portion of the tube 90. When lined up as such,this allows no compressed air or only a small amount of compressed airin the plenum 62 to flow into and down through the tube 90 andultimately into the wheelspace 68. This reduction in the amount ofcooling air provided to the wheelspace 68 allows the temperature of thewheelspace 68 to increase by way of the causes previously mentioned.

In accordance with embodiments of the invention, each wheelspace 68 mayutilize a plurality of the actuator 78 and valve 82 combinations asshown in FIG. 2 and described hereinabove. As such, the synch ring 76,if utilized, may be used to cause the simultaneous activation of theplurality of actuator 78 and valve 82 combinations that encircle theentire circumference of the turbine section 14 (FIG. 1) and correspondto a single wheelspace 68, to thereby properly control the temperatureof that wheelspace 68 to a desired value. Each wheelspace 68 may haveits own dedicated synch ring 76.

In FIG. 3 is another embodiment of the invention that is somewhatsimilar to the embodiment of FIG. 2. Thus, as between FIGS. 2 and 3,like reference numbers refer to like elements. In FIG. 3 in place of thetube 90 the shaft 80 extends downward (as viewed in FIG. 3) through theentire height of the hollow nozzle 64 and into the diaphragm 66. At thebottom of the shaft 80 is a movable (e.g., rotatable) linkage 100 thatconnects to a cooling air control valve 102 in the form of a rotatingvalve ring with one or more spaced apart openings 104 formed therein.Similar to the embodiment of FIG. 2, the cooling air control valve 102may comprise other suitable types of valves, such as a butterfly valve,a gate valve, or a ball valve. The rotating valve ring may encircle theentire circumference of the turbine section 14 of the gas turbine 10(FIG. 1). Each opening 104 is in fluid communication with the wheelspace68 through a corresponding hole 106 formed (e.g., drilled) in a solidmetal portion of the diaphragm 66.

In operation, when the microprocessor 50 determines that thethen-current temperature of a particular wheelspace 68 is greater than adesired or acceptable upper value, the microprocessor activates theactuator control signal on the signal path 54, which ultimately causesthe shaft 80 to move (e.g., rotate) and causes the linkage 100 to move(e.g., rotate) until each of the openings 104 in the rotating valve ring102 lines up (either fully or partially) with the corresponding one ofthe holes 106. When the openings 104 are lined up as such, this allowsan amount of the cooling compressed air in the diaphragm 66 to flowthrough the lined up openings 104 and into and down through the holes106 (as viewed in FIG. 3) and ultimately into the wheelspace 68, therebyreducing the temperature of the wheelspace 68 to an acceptable value.Similar to the embodiment of FIG. 2, once the microprocessor 50determines that the wheelspace temperature is below an upper value, themicroprocessor activates the actuator control signal on the signal path54 to cause the cooling air control valve 102 to move (e.g., rotate)and, thus, cause the openings 104 in the rotating valve ring 102 to notalign, or only partially align, with the corresponding holes 106. Thisstops or reduces the flow of cooling compressed air to the wheelspace68.

Also, when the microprocessor 50 determines that the then-currenttemperature of a particular wheelspace 68 is less than a desired oracceptable lower value, the microprocessor activates the actuatorcontrol signal on the signal path 54, which ultimately causes the shaft80 to move (e.g., rotate) and causes the linkage 100 to move (e.g.,rotate) until each of the openings 104 in the rotating valve ring 102does not line up (either fully or partially) with the corresponding oneof the holes 106. When the openings 104 are lined up as such, thisallows no cooling compressed air or only a small amount of coolingcompressed air into the diaphragm 66 to flow through the lined upopenings 104 and into and down through the holes 106 (as viewed in FIG.3) and ultimately into the wheelspace 68. This allows the temperature ofthe wheelspace 68 to increase to a desired or acceptable value by way ofthe causes previously mentioned.

Embodiments of the invention provide for improved control of turbinewheelspace temperature through control of the cooling compressed airflowprovided to the wheelspace 68 largely separate and apart from thecooling airflows delivered to other gas turbine components. Thus,embodiments of the invention have no negative impact on, and are notinfluenced by, the cooling airflow provided separately to these othergas turbine components and any leakages associated therewith.Embodiments of the invention may be applied to the wheelspaces of gasturbines either as a modification (retrofit) or as part of an originaldesign.

Embodiments of the invention also provide for reduction in the use ofparasitic secondary airflows, thereby increasing gas turbine efficiencyand power output. By using compressor extraction flow modulation coupledwith the microprocessor 50 as part of a feedback control system, areduced amount of compressed airflow can be delivered to the wheelspaces68 regardless of variations in ambient conditions, load, andmachine-to-machine variations in leakage flows.

While the invention has been described in detail in connection with onlya limited number of embodiments, it should be readily understood thatthe invention is not limited to such disclosed embodiments. Rather, theinvention can be modified to incorporate any number of variations,alterations, substitutions or equivalent arrangements not heretoforedescribed, but which are commensurate with the spirit and scope of theinvention. Additionally, while various embodiments of the invention havebeen described, it is to be understood that aspects of the invention mayinclude only some of the described embodiments. Accordingly, theinvention is not to be seen as limited by the foregoing description, butis only limited by the scope of the appended claims.

1. Apparatus for controlling an amount of cooling air provided to awheelspace of a turbine section of a gas turbine, the apparatuscomprising: a sensor that senses a temperature of the wheelspace andprovides a sensed temperature signal; a processor, responsive to thesensed temperature signal, that determines if the temperature of thewheelspace exceeds a desired value; and if the temperature of thewheelspace exceeds the desired value, the processor activates anactuator control signal to control movement of a cooling air controlvalve to allow a greater amount of cooling air sourced from a compressorsection of the gas turbine or from a cooling air cooler which receivesair from the compressor section of the gas turbine to flow to thewheelspace, thereby cooling the temperature of the wheelspace.
 2. Theapparatus of claim 1, the cooling air being provided to a plenum inwhich the cooling air control valve is located.
 3. The apparatus ofclaim 1, the actuator control signal provided to a first actuator thatcontrols movement of an output shaft of the first actuator in responseto the actuator control signal, the output shaft of the first actuatorbeing connected with the cooling air control valve, the movement of thefirst actuator output shaft controlling the movement of the cooling aircontrol valve to allow the cooling air to flow to the wheelspace.
 4. Theapparatus of claim 3, the cooling air control valve being connected witha tube having one or more openings that align with one or more openingsin the cooling air control valve to allow the cooling air to flow to thewheelspace when the temperature of the wheelspace exceeds the desiredvalue.
 5. The apparatus of claim 3, the first actuator output shaft andthe cooling air control valve being rotatable.
 6. The apparatus of claim1, a second actuator being connected to the actuator control signal, thesecond actuator having an output connected to the first actuator thatcontrols movement of an output shaft of the second actuator in responseto the actuator control signal, the output shaft of the first actuatorbeing connected with the cooling air control valve, the movement of thefirst actuator output shaft controlling the movement of the cooling aircontrol valve to allow the cooling air to flow to the wheelspace.
 7. Theapparatus of claim 6, the second actuator comprising one of a motor orhydraulic actuator.
 8. The apparatus of claim 1, the cooling air beingprovided by a pipe, duct or hole to a plenum in which the cooling aircontrol valve is located.
 9. The apparatus of claim 1, a plurality offirst actuators being connected to the actuator control signal, each ofthe plurality of first actuators having an output connected to a synchring that simultaneously controls movement of an output shaft of each ofthe plurality of first actuators in response to the actuator controlsignal, the output shaft of each of the plurality of first actuatorsbeing connected to a corresponding one of a plurality of the cooling aircontrol valves, the movement of each one of the first actuator outputshafts controlling the movement of the corresponding cooling air controlvalve to allow the cooling air to flow to the wheelspace.
 10. Theapparatus of claim 1, the cooling air control valve comprising arotating valve ring located within a diaphragm, the cooling air beingprovided to the diaphragm in which the rotating valve ring is located.11. Apparatus for controlling an amount of cooling air provided to awheelspace of a turbine section of a gas turbine, the apparatuscomprising: a sensor that senses a temperature of the wheelspace andprovides a sensed temperature signal; a processor, responsive to thesensed temperature signal, that determines if the temperature of thewheelspace is below a desired value; and if the temperature of thewheelspace is below the desired value, the processor activates anactuator control signal to control movement of a cooling air controlvalve to allow a lesser amount of cooling air sourced from a compressorsection of the gas turbine or from a cooling air cooler which receivesair from a compressor section of the gas turbine to flow to thewheelspace, thereby allowing the temperature of the wheelspace toincrease.
 12. The apparatus of claim 11, the cooling air being providedto a plenum in which the cooling air control valve is located.
 13. Theapparatus of claim 11, the actuator control signal provided to a firstactuator that controls movement of an output shaft of the first actuatorin response to the actuator control signal, the output shaft of thefirst actuator being connected with the cooling air control valve, themovement of the first actuator output shaft controlling the movement ofthe cooling air control valve to allow the cooling air to flow to thewheelspace.
 14. The apparatus of claim 13, the cooling air control valvebeing connected with a tube having one or more openings that align withone or more openings in the cooling air control valve to allow thecooling air to flow to the wheelspace when the temperature of thewheelspace is below the desired value.
 15. The apparatus of claim 13,the first actuator output shaft and the cooling air control valve beingrotatable.
 16. The apparatus of claim 11, a second actuator beingconnected to the actuator control signal, the second actuator having anoutput connected to the first actuator that controls movement of anoutput shaft of the second actuator in response to the actuator controlsignal, the output shaft of the first actuator being connected with thecooling air control valve, the movement of the first actuator outputshaft controlling the movement of the cooling air control valve to allowthe cooling air to flow to the wheelspace.
 17. The apparatus of claim16, the second actuator comprising one of a motor or hydraulic actuator.18. The apparatus of claim 11, the cooling air being provided by a pipe,duct or hole to a plenum in which the cooling air control valve islocated.
 19. The apparatus of claim 11, a plurality of first actuatorsbeing connected to the actuator control signal, each of the plurality offirst actuators having an output connected to a synch ring thatsimultaneously controls movement of an output shaft of each of theplurality of first actuators in response to the actuator control signal,the output shaft of each of the plurality of first actuators beingconnected to a corresponding one of a plurality of the cooling aircontrol valves, the movement of each one of the first actuator outputshafts controlling the movement of the corresponding cooling air controlvalve to allow the cooling air to flow to the wheelspace.
 20. Theapparatus of claim 11, the cooling air control valve comprising arotating valve ring located within a diaphragm, the cooling air beingprovided to the diaphragm in which the rotating valve ring is located.